Billie Joe Armstrong Joined the Replacements Onstage at Coachella

Coachella's second weekend took off last night with repeated sets by many of the artists who played last weekend. Among them was '80s greats the Replacements, who are playing a few reunion shows at various festivals this summer.

But last night the Mats pulled out a surprise, bringing Green Day's Billie Joe Armstrong out for a few songs. You can see them cover 'I Will Dare' (from their classic 1984 album 'Let It Be') above. Below they tear through 'I.O.U.' from 1987's 'Pleased to Meet Me.'

According to sources, Replacements frontman Paul Westerberg walked onstage with a cane, and played part of the band's set sitting on a couch, which you can see below. But nobody's really sure if Westerberg was hurt (rumors were going around that he may have hurt his back), or if the band was just f---ing around, which they've been known to do.